1. Field of the Invention
The present invention relates generally to a new and improved apparatus for vacuum painting strip materials, and specifically, to a new and improved vacuum painting apparatus having a continuous feed of strip materials to be painted.
2.Description of the Prior Art
It is known in the prior art, for example, in the U.S. Pat. No. 3,084,662 to Afton C. Badger, to provide an apparatus having a continuous feed and which uses vacuum technology.
The basic principle of the Badger-type coating system involves the confinement of a mass of coating material in an application chamber above which a vacuum is formed so that a continuous flow of air will be induced into the coating chamber around the periphery of units of strip material positioned within entrance and exit ports, to remove excess amounts of coating material on surface portions of units of strip material exiting the chamber, and at least partly to dry the coating on the exiting surfaces. The Badger system produces a finished coating that is very uniform and, with certain coating materials, nearly dry.
Since the introduction of the Badger coating concept, some minor improvements have been made in the technology, including utilizing sliding gates at the entrance and exit ports of the application chamber to expedite the changing of entrance and exit port dimensions. However, after the positions of these sliding gates are adjusted, they are held rigidly in the adjusted position to provide exit and entrance ports of fixed dimensions. Fixed entrance and exit port dimensions would be satisfactory if the dimensions of strip material being conveyed through the coating chamber were always constant. As is well known, many types of strip material, particularly fencing lumber strips and the like, have dimensions which can vary substantially from strip to strip. Where such variations in strip material dimensions are encountered, the use of rigidly fixed entrance and exit port dimensions can result in an oversize unit binding up in the application chamber.
More importantly, the Badger coating system technology relies on maintaining a small air gap between surface portions of units of strip material and the sides of the exit port so that accurate, uniform control over the thickness and the integrity of the coating on the strip material can be maintained. Obviously, units of strip material having dimensions substantially larger than normal would at least have one surface touch one of the edges of the exit port marring the coating on the touching surface. This marring is particularly undesirable where the coating is a finish coat of paint and is especially objectionable if marring occurs on the top surface of the board due to contact with the top edge of the exit port.
In another prior art patent, U.S. Pat. No. 4,333,417 to Neal H. Camp, et al, there is provided a vacuum painting system which uses a dimensional sensing feature to adjust one of the exit port gates to accommodate variations in the size of the object to be painted. The Camp, et al patent also provides a masking element within the chamber for preventing the application of coating to at least a part of one surface of a unit of strip material passing through the chamber.
However, neither of these patents exemplary of the prior art takes into consideration, or compensates for, the fact that most strip materials will have a bend or twist along their lengths which could cause a binding of the strip material in the entry and exit ports if not accounted for. Moreover, neither of those prior art patents takes into consideration that the apparatus should avoid wiping of the painted surfaces, other than by making the entry and exit ports larger.
It is therefore the primary object of the present invention to provide a new and improved vacuum painting apparatus which compensates for bending or twisting of the strip material being continuously fed into the apparatus.
It is another object of the present invention to provide a new and improved vacuum painting apparatus which substantially eliminates any wiping of the painted surfaces.